Real-time automated heterogeneous proppant placement

Abstract

A system and a method for heterogeneous proppant placement in a fracture ( 12 ) in a subterranean formation ( 18 ) are disclosed. The system includes a delivery system ( 10 ) for delivering proppant and treatment fluid to the fracture ( 12 ), a sensor ( 20 ) for measuring geometry of the fracture and a computer ( 24 ) in communication with the sensor ( 20 ). The computer ( 24 ) includes a software tool for real-time design of a model ( 38 ) for heterogeneous proppant placement in the fracture ( 12 ) based on data from the sensor ( 20 ) measurements and a software tool for developing and updating a proppant placement schedule ( 42 ) for delivering the proppant and treatment fluid to the fracture ( 12 ) corresponding to the model. A control link between the computer ( 24 ) and the delivery system ( 10 ) permits the delivery system ( 10 ) to adjust the delivery of the proppant and treatment fluid according the updated proppant placement schedule.

1. A method of heterogeneous proppant placement in a subterranean formation, comprising the steps of:
 (a) designing an initial model for a heterogeneous proppant placement in a fracture in the formation; 
 (b) developing an initial proppant placement schedule for delivering proppant and treatment fluid to the fracture predicted to obtain the initial model; 
 (c) beginning delivery of the proppant to the fracture according to the initial proppant placement schedule; 
 (d) taking real-time fracture geometry measurements during the proppant delivery; 
 (e) updating the model according to the geometry measurements; 
 (f) updating the proppant placement schedule according to the updated model and delivering the proppant according to the updated proppant placement schedule; and 
 (g) repeating steps (d) through (f) in real-time until the proppant delivery is complete. 
 
   
   
     2. The method of  claim 1  wherein parameters for the model comprise formation mechanical properties selected from the group consisting of Young's modulus, Poisson's ratio, formation effective stress and a combination thereof. 
   
   
     3. The method of  claim 1  wherein the proppant is delivered in slugs. 
   
   
     4. The method of  claim 3  wherein the proppant placement schedule comprises slugs of proppant alternated with a proppant-lean fluid. 
   
   
     5. The method of  claim 1  comprising phasing the delivery of the proppant in a programmable optimum density (POD) blender. 
   
   
     6. The method of  claim 1  comprising phasing the delivery of the proppant in a tub blender. 
   
   
     7. The method of  claim 1  comprising varying a fluid delivery flowrate. 
   
   
     8. The method of  claim 1  wherein the delivery comprises automatically controlling pumping and blending of proppant and treatment fluid. 
   
   
     9. The method of  claim 1  wherein the design and updating of the model comprise determining the amount of proppant for delivery. 
   
   
     10. The method of  claim 1  wherein the design and updating of the model comprise determining the fracture dimensions. 
   
   
     11. The method of  claim 1  wherein the treatment fluid comprises a heterogeneity trigger for heterogeneous proppant placement. 
   
   
     12. The method of  claim 11  wherein the heterogeneity trigger comprises a chemical reactant heterogeneity trigger. 
   
   
     13. The method of  claim 11  wherein the heterogeneity trigger comprises a physical heterogeneity trigger. 
   
   
     14. The method of  claim 11  wherein the heterogeneity trigger comprises a fibrous heterogeneity trigger. 
   
   
     15. The method of  claim 1  further comprising forming clusters of proppant with open channels between the clusters. 
   
   
     16. The method of  claim 1  further comprising delivering fibers to the fracture. 
   
   
     17. The method of  claim 1  wherein the proppant placement schedule further comprises varying a proppant concentration profile in the treatment fluid. 
   
   
     18. The method of  claim 17  wherein the proppant concentration profile is varied according to a dispersion method. 
   
   
     19. The method of  claim 17  wherein the proppant concentration profile is varied to inhibit the formation of pinch points. 
   
   
     20. The method of  claim 1  wherein the geometric measurements comprise seismic monitoring. 
   
   
     21. The method of  claim 1  wherein the updating the model comprises determining fracture growth according to material balance calculations, pressure response measurements, seismic event measurements or a combination thereof. 
   
   
     22. The method of  claim 1  further comprising allowing the fracture to close. 
   
   
     23. The method of  claim 1  further comprising producing fluids from the formation. 
   
   
     24. A system for heterogeneous proppant placement in a fracture in a subterranean formation, comprising:
 a delivery system for delivering proppant and treatment fluid to the fracture; 
 a sensor for measuring geometry of the fracture; 
 a computer in communication with the sensor, comprising:
 a software tool for real-time design of a model for heterogeneous proppant placement in the fracture based on data from the sensor measurements; and 
 a software tool for developing and updating a proppant placement schedule for delivering the proppant and treatment fluid to the fracture corresponding to the model; and 
 
 a control link between the computer and the delivery system for delivery of the proppant and treatment fluid according the updated proppant placement schedule. 
 
   
   
     25. The heterogeneous proppant placement system of  claim 24  wherein the delivery system comprises a pump. 
   
   
     26. The heterogeneous proppant placement system of  claim 24  wherein the delivery system comprises a mixer. 
   
   
     27. The heterogeneous proppant placement system of  claim 24  wherein the delivery system comprises a blender. 
   
   
     28. The heterogeneous proppant placement system of  claim 27  wherein the blender comprises a programmable optimum density (POD) blender. 
   
   
     29. The heterogeneous proppant placement system of  claim 27  wherein the blender comprises a tub blender. 
   
   
     30. The heterogeneous proppant placement system of  claim 24  wherein the sensor is selected from the group consisting of pressure sensor, seismic sensor, tilt sensor, radioactivity sensor, magnetic sensor and electromagnetic sensor. 
   
   
     31. The heterogeneous proppant placement system of  claim 24  wherein the sensor comprises an array of sensors. 
   
   
     32. The heterogeneous proppant placement system of  claim 24  wherein the sensor comprises a noisy particulate material and a sensor for detecting a detonation, ignition or exothermic reaction of the noisy particulate material. 
   
   
     33. The heterogeneous proppant placement system of  claim 24  wherein the proppant comprises a device for actively transmitting data for locating the position of the transmitting device and the sensor comprises a sensor for receiving the transmitted location data. 
   
   
     34. A method, comprising:
 (a) designing an initial model for a heterogeneous proppant placement in a fracture in a formation, wherein the heterogeneous proppant placement includes clusters of high proppant concentration and open channels between the clusters; 
 (b) developing an initial proppant placement schedule for delivering proppant and treatment fluid to the fracture predicted to obtain the initial model; 
 (c) beginning delivery of the proppant to the fracture according to the initial proppant placement schedule, wherein the proppant placement schedule comprises alternating proppant-rich slugs and proppant lean stages; 
 (d) taking real-time fracture geometry measurements during the proppant delivery; 
 (e) updating the model according to the geometry measurements; 
 (f) updating the proppant placement schedule according to the updated model and delivering the proppant according to the updated proppant placement schedule; and 
 (g) repeating steps (d) through (f) in real-time until the proppant delivery is complete. 
 
   
   
     35. The method of  claim 34 , wherein developing the initial proppant placement schedule comprises determining a downhole proppant slug profile, inverting a solution to a slug dispersion problem, and determining a surface proppant concentration for the proppant-rich slugs according to the downhole proppant slug profile and the solution to the slug dispersion problem. 
   
   
     36. The method of  claim 35 , wherein the solution to the slug dispersion problem utilizes a dispersion coefficient Ez according to:
     Ez =( v   0   R   0 ) 2 /48 D;   
 
     wherein v 0  is a velocity of the treatment fluid, R 0  is a radius of a treatment tube, and D is a diffusion coefficient. 
   
   
     37. The method of  claim 35 , wherein the heterogeneous proppant placement comprises proppant pillars in the fracture, the method further comprising allowing the fracture to close, monitoring the formation for micro-seismic events, determining a geometry of the fracture according to the micro-seismic events, and updating the initial model according to the geometry of the fracture. 
   
   
     38. The method of  claim 34 , wherein updating the proppant placement schedule includes constraining a proppant lean stage to a relationship:
     t   noslug   *Q   rate <2 *w   frac   *H   frac   
 
     wherein t noslug  is a time to pump the proppant lean stage, where Q rate  is a pumping rate of the proppant lean stage, wherein w frac  is a width of the fracture, and wherein H frac  is a height of the fracture. 
   
   
     39. The method of  claim 38 , wherein constraining the proppant lean stages to the relationship comprises adjusting at least one of the time to pump the proppant lean stage, the pumping rate of the proppant lean stage, and a fluid volume of the proppant lean stage. 
   
   
     40. The method of  claim 34 , wherein the heterogeneous proppant placement comprises a plurality of localized proppant clusters in the fracture. 
   
   
     41. The method of  claim 40 , wherein the proppant placement schedule further includes alternating a fracturing fluid between low viscosity waterfrac fluid and a low viscosity viscoelastic fluid.